SETLOCAL
Begins localization of environment changes in a batch file. Environment
changes made after SETLOCAL has been issued are local to the batch file.
ENDLOCAL must be issued to restore the previous settings. When the end
of a batch script is reached, an implied ENDLOCAL is executed for any
outstanding SETLOCAL commands issued by that batch script.

SETLOCAL

If Command Extensions are enabled SETLOCAL changes as follows:

SETLOCAL batch command now accepts optional arguments:
ENABLEEXTENSIONS / DISABLEEXTENSIONS
enable or disable command processor extensions. See
CMD /? for details.
ENABLEDELAYEDEXPANSION / DISABLEDELAYEDEXPANSION
enable or disable delayed environment variable
expansion. See SET /? for details.
These modifications last until the matching ENDLOCAL command,
regardless of their setting prior to the SETLOCAL command.

The SETLOCAL command will set the ERRORLEVEL value if given
an argument. It will be zero if one of the two valid arguments
is given and one otherwise. You can use this in batch scripts
to determine if the extensions are available, using the following
technique:

VERIFY OTHER 2>nul
SETLOCAL ENABLEEXTENSIONS
IF ERRORLEVEL 1 echo Unable to enable extensions

This works because on old versions of CMD.EXE, SETLOCAL does NOT
set the ERRORLEVEL value. The VERIFY command with a bad argument
initializes the ERRORLEVEL value to a non-zero value.